Compactor System And Methods

ABSTRACT

A compactor system includes a tipped drum having a plurality of tips, and a drum axle rotatably coupling the tipped drum to a frame. The compactor system further includes a sensor configured to sense a parameter indicative of a height of the drum axle above a surface of a material substrate, and an electronic control unit configured to output a compaction progress signal responsive to inputs from the sensor. Related methods of preparing a work area with a compactor system, and determining a compaction state of a material substrate, are also disclosed.

TECHNICAL FIELD

The present disclosure relates generally to compactor systems andmaterial compaction strategies, and relates more particularly tomonitoring compaction progress by way of sensor data indicative of axleheight of a tipped drum compactor.

BACKGROUND

A wide variety of different compacting systems are used in thepreparation of earthen fill and compaction of other materials in civilengineering projects such as construction, road building and landfillactivities. Self-propelled two-wheel and four-wheel compactors,tow-behind systems, and others are well known and widely used. Engineershave recognized for many years that the capacity of substrate materialsto remain stable over time, support loads or serve as a barrier toliquids, as well as other properties, can depend in significant partupon compacting a given material to a certain compaction state. Simplypassing a compactor over a work area will tend to increase the relativecompaction state of the resident material. Thus, to some extentcompactor coverage is one metric which has been used to enable anoperator or site manager to estimate that a target compaction state hasbeen achieved. While knowing how many times a compactor has traversed agiven region of a work area can be useful information, many moderncompaction projects require a more sophisticated understanding of theactual compaction state or compaction response of material.

Different materials may have a widely varying “compaction response” orchange in properties resulting from coverage with a compactor machine.For instance, sandy or granular soils tend to exhibit a different changein relative compaction state than do clayey soils each time a compactoris passed over a given region. Local variations in material compositionor moisture content within a work area, as well as changes in moisturecontent over time can also result in non-uniformity in compaction stateeven where compactor coverage has been uniform. In addition to projectsuccess depending upon satisfaction of compaction specifications,payments or bonuses to contractors can also be based on the quality andtimeliness of a particular compaction job. Like many heavy-dutyconstruction machines, compactors can be quite expensive to operate, andthus unnecessary work or remedial actions create undesired expense. Forthe foregoing and other reasons, there is often a premium on machinesand/or operators capable of doing enough work with a compactor system tomeet a predefined goal, but avoiding any substantial wasted effort.

To this end, various strategies are known which provide information toan operator or site manager which is indicative of a compaction state ofmaterial, apart from merely how many times the material has beentraversed by a compactor. Nuclear density gauges are used to evaluatedensity of substrate material after coverage with a compactor. Whilesuch mechanisms are fairly precise, density of compacted material alonemay not be the factor of most interest. Moisture content can affectdensity measurements, and may change over time due to precipitation andevaporation, resulting in material presumed to be ideally compactedbased on density measurements, but which in fact is not. Measurements ofthe depth of ruts left by machines traveling over a compacted surface orsimilar tests are also used, and in some jurisdictions serve as aprimary compaction specification. Rut depth measurements, however, oftenrequire manual activities by personnel at a work site and/or onlyprovide a snapshot of the compaction state of the material at onelocation. Moreover, forming ruts over the entire surface of a work areawith a machine having certain specifications, and then measuring rutdepth, is impractical. So called “walk-out” testing has also been widelyused, in which a tipped drum compactor is driven onto a compactedsurface and visual inspection used to determine whether or not the drumtips substantially penetrate a compacted surface. If not, the compactedmaterial may be roughly estimated to be sufficiently compacted.

Still other strategies leverage the difference between an actual radiusof a compacting drum and an effective rolling radius. One example ofsuch an approach is disclosed in commonly owned U.S. Pat. No. 7,428,455to Corcoran. Indicating compaction by effective rolling radius has beenshown to be a viable, and in some instances superior, approach ascompared with other techniques. There remains room for still furtherimprovements, however.

SUMMARY OF THE DISCLOSURE

In one aspect, a method of preparing a work area with a compactor systemhaving a tipped drum includes compacting a material substrate within thework area at least in part by moving the compactor system such that anouter surface of the tipped drum rotates in contact with the materialsubstrate. The method further includes supporting the tipped drum onradially projecting drum tips such that the outer surface of the tippeddrum is elevated from the compacted material substrate, and sensing aparameter indicative of an axle height of the tipped drum relative to asurface of the compacted material substrate during supporting the tippeddrum. The method further includes outputting a compaction progresssignal responsive to the sensed parameter.

In another aspect, a method of determining a compaction state of amaterial substrate includes sensing a parameter indicative of an axleheight of a compactor having a tipped drum supported by a plurality ofradially projecting drum tips upon a surface of a compacted materialsubstrate, and receiving sensor data associated with the sensedparameter at an electronic control unit. The method further includesoutputting a signal from the electronic control unit which is indicativeof compaction state of the compacted material substrate, responsive tothe sensor date.

In still another aspect, a compactor system includes a frame, and atipped drum defining an axis of rotation and having a plurality of tipsradially projecting from a cylindrical outer drum surface. The compactorsystem further includes a drum axle rotatably coupling the tipped drumto the frame, and a sensor configured to sense a parameter indicative ofa height of the drum axle above a surface of a material substrate, andan electronic control unit. The electronic control unit is coupled witha sensor and configured to output a compaction progress signalresponsive to inputs from the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side diagrammatic view of a compactor system, according toone embodiment;

FIG. 2 is a side diagrammatic view of a tipped compactor drum supportedupon a substrate, at two different locations;

FIG. 3 is a pictorial view of a display illustrating mapped compactionstate, according to one embodiment; and

FIG. 4 is a flowchart illustrating portions of a control/monitoringroutine, according to one embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a compactor system 10 including acompactor 11, according to the present disclosure. Compactor system 10is shown in the context of a self-propelled four drum compactor having aframe 12 which includes a front frame unit 14 and a back frame unit 16,coupled together at an articulation joint 18. An operator cab 20 ismounted upon frame 12 and includes an operator control station 21 fromwhere an operator can control activities of compactor system 10, asfurther described herein. Compactor 11 may be equipped with an implement36 such as a blade or the like for purposes well known in the art. InFIG. 1, two tipped drums, including a right front drum 24 and a rightback drum 22 are shown, each of which includes a plurality of tips 26projecting from a cylindrical outer drum surface 28. It should beunderstood that compactor 11 may also include a left front drum and aleft back drum, which are hidden from view in the FIG. 1 illustration.Tips 26 may be any of a wide variety of known drum trip configurations,including conventional sheep's foot, pad foot, or some other tip design,and it should be understood that the present disclosure is applicable totipped drum compactor systems without limitation to any particular tipstyle.

In a similar vein, it should be understood that the machineconfiguration shown in FIG. 1 is illustrative only. A wide variety oftipped drum compacting systems may be advantageously designed andoperated in accordance with the teachings set forth herein. For example,rather than a four drum self-propelled compactor system, compactorsystem 10 might include a tow-behind tipped drum compactor, a singledrum compactor having a set of rearwardly mounted ground engagingpropulsion wheels, or still another type of compactor. Each of tippeddrums 22 and 24 may be rotatably coupled with frame 12 by way of a drumaxle, one of which is shown and identified via reference numeral 30 inconnection with tipped drum 22, having an axis of rotation A. Compactorsystem 10 is shown in FIG. 1 supported upon a material substrate Zhaving a surface S. Substrate Z may include soil, landfill trash, oranother type of material, and tipped drums 22 and 24 are positioned suchthat cylindrical outer surface 28 contacts surface S, and tips 26penetrate through surface S into the material of substrate Z. As will befurther apparent from the following description, compactor system 10 maybe uniquely configured to monitor and/or control compacting activitieswithin a work area, and enable an operator or site manager, or automatedsystem to control compactor system 10 such that target compactionspecifications for a particular project are met and unnecessary effortis reduced or avoided.

To this end, compactor system 10 may include a control system 39 havinga sensor 32 configured to sense a parameter indicative of a height ofdrum axle 30 above surface S. Sensor 32 may include a signal transducerconfigured to sense a transmitted signal, or component of a transmittedsignal, reflected by surface S. In the illustrated embodiment, a singlesensor 32 is shown coupled with and resident on frame 12. In otherembodiments, additional sensors such as a front sensor (not shown)associated with front drum 24 might be used, or individual sensorslocated in proximity to each compacting drum for a total of foursensors. In one practical implementation strategy, sensor 32 may belocated at or close to a center point of axle 30, at or close to alongitudinal centerline of frame 12. The transmitted signal may includea sonic signal, an RF signal, or a laser signal, for example,transmitted via a transmitter 34 mounted with sensor 32 in a housing 38.Sensor 32 may include a non-contact sensor such as the examples notedabove. In other embodiments, a gauge wheel, skid or the like might becoupled with frame 12, and configured to change vertical positionresponsive to changes in axle height of axle 30 above surface S, andoutput a signal indicative of axle height and/or changes therein. Agauge wheel or the like might be understood as a direct mechanicalsensing mechanism, in contrast to the non-contact sensing mechanismsnoted above. In still other embodiments, information received from aglobal positioning system (GPS) or a local positioning system might alsobe used in monitoring axle height. Control system 39 may further includea position sensor 46 resident on compactor 11 which receives global orlocal positioning data, potentially used in axle height monitoring asmentioned above, but also used in establishing and tracking geographicposition of compactor 11 within a work area. In one embodiment, furtherdescribed herein, data received via position sensor 46 may be linkedwith data received from sensor 32 to map position data of compactorsystem 10 received via sensor 46 to axle height data received fromsensor 32, for purposes which will be apparent from the followingdescription.

Control system 39 may further include an electronic control unit 40which includes at least one data processor 42, and a computer readablememory 44. Electronic control unit 40 may be coupled with sensor 32, andalso with position sensor 46, and may be configured to output a signalresponsive to inputs from sensor 32, as further described herein. Adisplay 48 also coupled with electronic control unit 40 may bepositioned at operator control station 29 to display various data to anoperator relating to axle height, machine position, relative compactionstate, or still other parameters. In the illustrated embodiment, controlsystem 39 is resident on compactor 11. It should be appreciated that inother embodiments, control system 39 or parts thereof might be locatedremotely from compactor 11, such as at an offsite management office. Insuch an embodiment, data gathered relating to position of compactor 11and axle height data might be transmitted to a remote computer,processed, and control commands sent to compactor 11 to direct anoperator to take or forego certain actions, or to direct compactor 11 toautonomously take or forego certain actions. Taking actions in responseto the axle height data and position data might include commencingtravel of compactor 11 within a work area, stopping travel of compactor11 within a work area, or redirecting or otherwise changing a plannedcompactor travel path or coverage pattern. Computer readable memory 44may store computer executable code comprising a control algorithm fordetermining a relative compaction state of material substrate Z and/ordetermining a change in relative compaction state, responsive to inputsfrom sensor 32, and the same or another algorithm for controlling ordirecting operation of compactor 11. In one embodiment, thedetermination of relative compaction state or changes therein may bebased at least in part upon a difference between an axle height of axle30 when material substrate Z is at a relatively lower compaction stateand an axle height of axle 30 when material substrate Z is at arelatively greater compaction state.

Referring now also to FIG. 2, those skilled in the art will be familiarwith the difference between the way a tipped drum may interact with amaterial substrate at a relatively uncompacted stated versus arelatively more compacted state. In particular, when a tipped drumcompactor initially commences compacting a material substrate, the drumtips will typically sink into the material such that the outer drumsurface of the tipped drum contacts the material substrate and compactsthe same. Meanwhile, penetration of the drum tips into the material willalso compact the material, from the bottom up. As compaction progresses,typically via additional compactor passes over a particular area of awork area, an increased compaction of the material substrate may resultin the drum tips penetrating the material less at each successive pass,such that the outer drum surface is actually elevated from a surface ofthe compacted material substrate. The present disclosure leverages thisphenomenon and an associated change in axle height, to determine arelative compaction state of the material and/or changes therein,enabling the monitoring of compaction progress.

In FIG. 1, compactor 11 is shown as it might appear during an initial orearly stage of compacting substrate Z where outer surface 28 contactssurface S, such as during a first pass across surface S. In FIG. 2tipped drum 22 is shown supported on substrate Z as it might appearafter compactor 11 has performed one or more initial passes, typicallymultiple passes, across surface S to compact substrate Z to a state atwhich outer surface 28 is elevated from surface S. It may thus be notedthat in FIG. 1, axle 30 is elevated a first, relatively lesser distancefrom surface S, whereas in FIG. 2 axle 30 is elevated a second,relatively greater distance from surface S. In FIG. 2, axle height isillustrated via reference letter D. One way in which the change in axleheight may be leveraged to determine a change in relative compactionstate is by comparing axle height D with a radius R of a circle definedby outer surface 28 about axis A. For instance, when compactor 11 isoperating under conditions similar to those depicted in FIG. 1, a heightof axle 30 above surface S within a footprint of drum 22 may be equal toradius R. When compactor 11 is operating under conditions similar tothose depicted in FIG. 2, axle height may be relatively greater thanradius R. Electronic control unit 40 may, in one embodiment, beconfigured to compare axle height D with radius R or a value indicativeof radius R, and output a signal responsive to the difference. Sinceinputs received by electronic control unit 40 from sensor 32 areindicative of axle height, the outputted signal from electronic controlunit 40 may also be understood as responsive to the sensor inputs. Infurther embodiments or extensions of such an embodiment, electroniccontrol unit 40 may output a signal based on an arithmetic differencebetween axle height D and radius R. When the arithmetic difference isequal to or greater than a predefined threshold, it may be determinedthat material substrate Z has been compacted part way or all the way toa specified target compaction state.

As discussed above, increasing the relative compaction state ofsubstrate Z may transition compactor 11 from a state in which outersurface 28 contacts surface S during rotating tipped drum 22 in contactwith surface S, to a state in which outer surface 28 is elevated fromsurface S during rotating tipped drum 22 in contact with surface S.Accordingly, the signal outputted from electronic control unit 40responsive to inputs from sensor 32 may be indicative of a relativecompaction state or change in relative compaction state of the materialcomprising substrate Z. Where determining or estimating relativecompaction state alone is desired, information pertinent to thedetermination or estimation, such as the weight of compactor 11, surfaceareas and numbers of drum tips 26, geometry of drum tips 26, and otherfactors such as soil composition and moisture, are known to thoseskilled in the art or may be determined empirically. Where determiningor estimating a change in relative compaction state is desired, a changein determined axle height between one compactor pass and a nextcompactor pass may be empirically related via prior field or laboratorytesting or simulation to a change in relative compaction state, for aparticular compactor system. Further, a simple determination that axleheight D is greater than radius R may be sufficient to determine thatcompaction progress is being made. It may further be appreciated that nochange in axle height will typically be detected until substrate Z hasbeen compacted sufficiently to elevate outer surface 28 above surface S.Monitoring of axle height may take continuously during operatingcompactor system 10, periodically, or only after detection of sometrigger or satisfaction of predetermined conditions. For example, in onestrategy axle height may be continuously monitored throughout acompacting procedure. In another strategy, axle height may be monitoredonly after, say, three compactor passes have occurred, while in stillanother strategy axle height might be monitored during a separate testrun after a site manager has estimated it is likely that the project isfinished but wishes to obtain assurance that specifications aresatisfied. In any of these examples, as well as others contemplatedherein, the signal outputted from electronic control unit 40 responsiveto inputs from sensor 42 may include a compaction progress signal,indicating that a predefined increase in relative compaction state orsatisfaction of predefined specifications has occurred. Thus, the term“compaction progress” as used herein may be understood to mean that someidentifiable interim goal or end goal has been achieved.

It may also be noted from FIG. 2 that tipped drum 22 is shown at twodifferent locations, the leftmost being in phantom, upon substrate S. Asalluded to above, in one embodiment control system 39 might beconfigured to periodically sense axle height when compactor 11 isoperating, such as at the two locations shown in FIG. 2. Monitoring ofaxle height may alternatively be essentially continuous such that axleheight measurements are determined while rotating tipped drum 22 incontact with material substrate Z throughout a compaction project. Ineither case, control system 39 may be configured to link position datareceived via position sensor 46 with the axle height data, such thatrelative compaction state may be mapped to geographic coordinates withina work area. Axle height at the leftmost location of drum 22 in FIG. 2might include a first distance, whereas axle height at the rightmostlocation might include a second distance, due to a local variation incompaction response, and the different axle heights or associatedcompaction state can be mapped to particular regions of the work area.

In one further embodiment, mapping relative compaction state may bebased upon a length coordinate and a width coordinate such that a workarea can be divided into cells, for example based on relative compactionstate thereof. Referring also now to FIG. 3, there is shown a pictorialview of display 48 illustrating graphical information which might bedisplayed to an operator or manager at a particular work site. In FIG.3, a work area X is shown in the process of being prepared and havingbeen compacted by at least one pass via compactor system 10, and wherecompactor system 10 is performing an additional pass over work area X.One strategy for dividing work area X into cells includes setting a cellwidth coordinate W which is approximately equal to a width of compactor11, and setting a length coordinate L for each of the cells which mayvary based upon average axle height, or determined relative compactionstate. Another way to understand the illustration in FIG. 3 is thatcompactor system 10 may proceed across a work area, and as axle heightdata is gathered, control system 39 may group together areas in whichthe axle height data indicates a similar relative compaction state, orsimilar change in relative compaction state as compared with proceedingcompactor passes. Thus, length coordinate L may be mutable whereas widthcoordinate W may be fixed. Alternatively, a fixed cell width and fixedcell length might be used. In the FIG. 3 illustration, displayinghorizontal lines within the individual cells may indicate that materialsubstrate Z is at a level=0 and has not been compacted sufficiently toelevate outer surface 28 from surface S. Intersecting diagonal linesindicates cells where material substrate Z has compacted to a level=1,sufficient to elevate surface 28 a first distance from surface S,signifying some compaction progress but not achievement of compactionspecifications. Non-intersecting diagonal lines indicate cells at alevel=2, where material substrate Z has compacted sufficiently such thatouter surface 28 is elevated a second, relatively greater distance,signifying achievement of compaction specifications. A variety of otherinformation display strategies might be used within the present context.For instance, a fixed grid/cell system for the work area might be used.A planned compactor travel path might also be displayed, and updated ifaxle height data indicates that certain regions need more work or thatcertain regions are finished. In one embodiment, a default compactortravel path may be based on uniform coverage, but changed upon discoveryof differentially compacting regions with a work area. Any of theinformation or graphics displayed on display 48 may be generated orupdated responsive to the signal outputted by electronic control 40 inresponse to inputs from sensor 32.

INDUSTRIAL APPLICABILITY

Referring now to FIG. 4, there is shown a flowchart 100 illustratingcertain steps in a control and monitoring process whereby a work areasuch as work area X is prepared via compactor system 10, or anothercompactor system as contemplated herein. The process of flowchart 100may start at step 110, and may proceed to step 120 at which compactorsystem 10 is operated. Commencing operation of compactor system 10 mayinclude compacting material substrate Z within work area X via movingcompactor system 10 such that outer surface 28 of tip drum 22 rotates incontact with material substrate Z. This initial step of operatingcompactor system 10 may include performing one or more, and typically atleast two, passes over all of work area X.

Subsequently, operating compactor system 10 may also include operatingcompactor system 10 where tipped drum 22 is supported on radiallyprojecting drum tips 26 such that outer surface 28 is elevated fromcompacted material substrate Z. This step may occur during subsequentpasses over work area X, such as a third, fourth, or fifth pass,depending upon material type or condition, compactor specifications, andother factors. Prior to or during operating compactor system 10 suchthat tipped drum is supported on drum tips 26, a signal may betransmitted from transmitter 34 toward surface S. The transmitted signalmay be reflected by surface S, and sensor 32 may sense the transmittedand reflected signal or components thereof at step 140. From step 140,the process may proceed to step 150 wherein electronic control unit 40may calculate axle height, estimate axle height, or otherwise determinea value indicative of axle height, in the manner described herein. Fromstep 150, the process may proceed to step 160 at which electroniccontrol unit 40 may output a compaction progress signal as describedherein. In response to the compaction progress signal, compactor 11 maybe directed via commands generated by electronic control unit 40 oranother computer, or a site operator, to continue as planned, change thecompactor coverage plan, cease operation, or take some other action.Such commands may be displayed in an operator format on display 48, orcommunicated via an alarm or still another mechanism. From step 160, theprocess may proceed to finish at step 170. Receipt of position data,linking the position data with the compaction progress signal orotherwise with the axle height data, and displaying information to anoperator or other party may occur during executing the routine offlowchart 100, in parallel, or subsequently.

Those skilled in the art will be familiar with conventional tests ofrelative compaction state and compaction response of material. The abovedescribed examples of nuclear density measurements, effective rollingradius, rut depth measurements, and walk-out tests, have all foundapplicability in various environments over the years. The presentdisclosure presents an alternative strategy, improving over conventionalapproaches in at least certain environments. The ability to sense axleheight directly enables an operator or site manager to continuously orperiodically monitor compaction progress in a manner not available, orat least not practicable with many traditional strategies. Nucleardensity measurements may be time consuming, require specializedequipment, and may even require specially trained technicians. Walk-outtests typically require visual observation of drum tip penetration. Notonly is visual observation inherently unreliable and qualitative only,it is typically necessary to halt compactor operation to allow anobserver to inspect the drum tip penetration. Further, since walk-out bydefinition is restricted to observations at one location at a time,trends in drum tip penetration over time and variance in drum tippenetration among different regions of a work area, limit the extent andpracticability of using walk-out to evaluate ongoing compaction progressor take action based on non-uniformity in compaction state of materialwithin a work area. The present disclosure can enable snapshotdeterminations of relative compaction state, an overall picture of how awork area is responding to compaction efforts, and analysis of trends incompaction response of material.

With regard to monitoring compaction state by way of effective rollingradius, while such strategies have been widely and advantageouslyapplied, and could even be integrated with the teachings of the presentdisclosure within a single system, effective rolling radius may in atleast certain instances require moving the associated compactor a traveldistance equal to or greater than one full circumference of thecompacting drum. The present disclosure allows compaction state to bemapped at a relatively high map resolution, in which a length of cellswithin a work area can be less than one full drum circumference.Moreover, implementing effective rolling radius approaches in four-wheelcompactors, while theoretically possible, may be complex from thestandpoint of processing data from the calculations for multiplerotating drums, or for other reasons. Rut depth measurements and similarstrategies leverage phenomena different from the penetration of multipledrum tips into a substrate, and like other conventional strategiesdiscussed herein, do not generally enable any robust determination orestimation of the shear strength of compacted material. The presentdisclosure may be applied to determine quantitative or qualitativemeasurements relating to shear strength, based upon known machineparameters and the extent to which drum tips penetrate into a compactedmaterial substrate.

The present description is for illustrative purposes only, and shouldnot be construed to narrow the breadth of the present disclosure in anyway. Thus, those skilled in the art will appreciate that variousmodifications might be made to the presently disclosed embodimentswithout departing from the full and fair scope and spirit of the presentdisclosure. Other aspects, features and advantages will be apparent uponan examination of the attached drawings and appended claims.

1. A method of preparing a work area with a compactor system having atipped drum comprising the steps of: compacting a material substratewithin the work area at least in part by moving the compactor systemsuch that an outer surface of the tipped drum rotates in contact withthe material substrate; supporting the tipped drum on radiallyprojecting drum tips such that the outer surface of the tipped drum iselevated from the compacted material substrate; sensing a parameterindicative of an axle height of the tipped drum relative to a surface ofthe compacted material substrate during supporting the tipped drum; andoutputting a compaction progress signal responsive to the sensedparameter.
 2. The method of claim 1 wherein the tipped drum is rotatablycoupled with a frame of a self-propelled compactor machine, and whereinthe step of sensing includes sensing the parameter by way of a sensorresident on the compactor machine.
 3. The method of claim 2 furthercomprising a step of transmitting a signal from a transmitter residenton the compactor machine toward the surface of the compacted materialsubstrate, and wherein the step of sensing includes sensing thetransmitted signal reflected by the surface.
 4. The method of claim 2wherein the step of supporting includes supporting the tipped drumduring rotating the tipped drum in contact with the compacted materialsubstrate.
 5. The method of claim 2 further comprising the steps ofreceiving position data of the compactor machine, and linking thereceived position data with the compaction progress signal.
 6. Themethod of claim 5 wherein the compaction progress signal includes asignal indicative of a relative compaction state of the materialsubstrate, and wherein the step of linking further includes mappingrelative compaction state to geographic coordinates defining a region ofthe work area.
 7. The method of claim 6 wherein mapping relativecompaction state further includes mapping relative compaction state at amap resolution based on a width coordinate, and a length coordinatewhich is equal to less than one full circumference of the outer surfaceof the tipped drum.
 8. The method of claim 1 further comprising thesteps of receiving data of the sensed parameter, determining a valueindicative of the axle height responsive to the data, and comparing thedetermined value with a value indicative of the radius of a circledefined by the tipped drum about an axis of rotation of the tipped drum,and wherein the step of outputting takes place responsive to adifference between the compared values.
 9. A method of determining acompaction state of a material substrate comprising the steps of:sensing a parameter indicative of an axle height of a compactor having atipped drum supported by a plurality of radially projecting drum tipsupon a surface of a compacted material substrate; receiving sensor dataassociated with the sensed parameter at an electronic control unit; andoutputting a signal from the electronic control unit which is indicativeof compaction state of the compacted material substrate, responsive tothe sensor data.
 10. The method of claim 9 wherein the step of sensingfurther includes sensing the parameter during moving the compactorwithin the work area.
 11. The method of claim 9 further comprising thesteps of receiving position data of the compactor, and linking theposition data with the sensor data, and wherein the step of receivingsensor data further includes receiving sensor data for a plurality ofseparate regions of the work area.
 12. The method of claim 9 whereinreceiving sensor data for the plurality of test regions further includesreceiving sensor data from a non-contact sensor resident on thecompactor.
 13. The method of claim 12 wherein the electronic controlunit is configured to compare a value indicative of the axle height witha reference value indicative of the radius of a circle defined by thetipped drum about an axis of rotation thereof, and further configured tooutput the signal responsive to a difference between the comparedvalues.
 14. A compactor system comprising: a frame; a tipped drumdefining an axis of rotation and having a plurality of tips radiallyprojecting from a cylindrical outer drum surface; a drum axle rotatablycoupling the tipped drum to the frame; a sensor configured to sense aparameter indicative of a height of the drum axle above a surface of amaterial substrate; and an electronic control unit coupled with thesensor, the electronic control unit being configured to output acompaction progress signal responsive to inputs from the sensor.
 15. Thecompactor system of claim 14 wherein the electronic control unit isconfigured to determine a value indicative of the height of the drumaxle responsive to the inputs, and further configured to compare thedetermined value with a reference value indicative of the radius of acircle defined by the tipped drum about the axis of rotation.
 16. Thecompactor system of claim 15 further comprising a transmitter coupledwith the frame and configured to transmit a signal toward the surface ofthe compacted material substrate.
 17. The compactor system of claim 16further comprising a self-propelled compactor which includes the frameand the tipped drum, and a position sensor coupled with the electroniccontrol unit, and wherein the transmitter, sensor, position sensor andelectronic control unit are resident on the self-propelled compactor.